Stream nutrient and agricultural land-use trends from 1971 to 2010 in Lake Ontario tributaries |
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| Affiliation: | 1. Environmental and Life Sciences Graduate Program, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 7B8, Canada;2. School of the Environment, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 7B8, Canada;3. Environment and Climate Change Canada, 657 Lakeshore Rd, Burlington, ON L7S 1A1, Canada;4. Ganaraska Region Conservation Authority, 2216 County Rd 28, Port Hope, Ontario L1A 3V8, Canada;1. School for Environment and Sustainability, University of Michigan, 440 Church Street, Ann Arbor, MI 48109, USA;2. U.S. Geological Survey, Great Lakes Science Center, 1451 Green Road, Ann Arbor, MI 48105, USA;3. National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory, 1431 Beach Street, Muskegon, MI 49441, USA;4. Department of Environmental Science, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA;5. U.S. Geological Survey, Great Lakes Science Center, Lake Erie Biological Station, 6100 Columbus Avenue, Sandusky, OH 43528, USA;1. University of Toledo, Department of Environmental Sciences, Toledo, OH 43606, USA;2. U.S. Geological Survey, Great Lakes Science Center, Ann Arbor, MI 48105, USA;3. Michigan State University, Department of Fisheries and Wildlife, East Lansing, MI 48823, USA;4. Central Michigan University, Department of Biology, Mount Pleasant, MI 48859, USA;1. Environmental Consulting and Technology, Inc., 2200 Commonwealth Blvd, Ann Arbor, MI 48105, USA;2. School for Environment and Sustainability, University of Michigan, Ann Arbor, MI 48104, USA;3. Graham Sustainability institute, University of Michigan, 214 S. State St., Ann Arbor, MI 48104, USA;4. Sustainable Engineering and the Built Environment, Arizona State University, 660 S. College Ave., Tempe, AZ 85281, USA;5. Food, Agricultural and Biological Engineering, Ohio State University, 590 Woody Hayes Dr., Columbus, OH 43210, USA;1. Dept. of Geography and Environmental Management, University of Waterloo, Waterloo, ON N2L 3G1, Canada;2. Dept. of Geography and Environmental Studies, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada;3. Ridgetown Campus, University of Guelph, Ridgetown, ON N0P 2C0, Canada |
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| Abstract: | Urbanization is generally recognized as the most widespread form of landuse/landcover change (LULC) within populated regions, including southern Ontario, and is often at the expense of surrounding agricultural land. However, changes in agricultural LULC within these peripheral regions should be considered when interpreting water quality changes in watersheds containing mixed LULC. The objectives of this study were to first, quantify changes in LULC within twelve Lake Ontario tributaries between 1971 and 2010, and secondly, to determine whether these changes co-occurred with changes in total phosphorus (TP) and nitrate?nitrogen (NO3-N) concentrations in streams. Water quality data were obtained from the Ontario Provincial Water Quality Monitoring Network while historical land use was reconstructed from agricultural census reports, historical land cover maps, and modern remotely sensed datasets. Urban cover increased, although percent increases in urban cover were small in the most agriculturally dominated watersheds (3–8%). The area of agriculture declined across all watersheds, yet the proportion of agricultural land dedicated to crop (corn, soybean, and wheat) production increased, including in the most urbanized watersheds (e.g. Mimico 89% urban; 2009–11). Total P concentrations in streams were highest at the urbanized watersheds, particularly in the 1970s, before declining in recent decades. In contrast, NO3-N concentrations were highest (>1.5 mg/L; 2000–10) within the most agricultural watersheds (e.g. Gages 71% agriculture) and have increased over the same period of row crop expansion. Further research is needed to determine the mechanisms behind the potential relationship between expanding row crop cover and stream NO3-N concentrations in southern Ontario. |
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